Current methods of directional control of automated guided vehicles generally rely on tracking an electromagnetically radiating wire buried in the factory or warehouse floor. This wire emanates a low frequency (less than 10 KHz) electromagnetic signal which is received by an antenna (or antennas) installed on the end(s) of the truck. Via a differential sensing scheme, the guidance control control attempts to maintain the truck centered on the floor wire. A schematic representation of this type of guidance system appears in FIG. 1. In a given factory installation, there may be numerous track wires, each operating at a different frequency to allow alternative steering paths over the floor area. End points and path junctures are generally sensed with truck-mounted magnetic reed switches. Permanent magnets are buried in the floor at juncture points to activate these switches.
The current wire-based guidance systems have inherent shortcomings. These shortcomings arise primarily from the requirement that the wire be buried in the factory or warehouse floor. This operation necessitates cleaning the concrete, marking the wire layout, cutting slots for the wires, installing the wires, sealing the slot with epoxy, and testing the system for continuity. This methodology is labor intensive, expensive, and is not amenable to alteration without a major effort. Also, since AGV technology is generally linked to flexible manufacturing systems, this inherent lack of adaptability is a major shortcoming. If the installation is in an existing warehouse, the task becomes even more difficult (and expensive) since the installation must usually be performed concurrent with normal warehousing operations.